Combo box

[jcaptchaos2]

I have an issue that I still can not figure out, I am scanning a bar code that has some code to place part of the scanned number in a combo box and the rest into a text box on the form. I want to prevent someone from typing in an incorrect number in the first combo box. I am told we need to use the scanner and I can not figure out a way to if the number is typed in to prevent an incorrect number. I know if I just used the combo box I could use the indexed option but since the code breaks the number up when scanning I think I need some type of after event code for the form, is this possible? I will give more details if someone has an idea.